KINGSTON, R.I. – June 16, 2015 – The bumpy ride over many roadway bridges in Rhode Island is not just uncomfortable for drivers and passengers, but it may be causing the bridge to deteriorate more quickly. So a University of Rhode Island engineering professor is evaluating 10 bridges in the state to better understand how the smoothness of concrete bridge decks can lengthen the lives of bridges and, ultimately, improve their safety.
“Concrete bridge decks often exhibit significantly more roughness than the roads leading into and away from them,” said Mayrai Gindy, URI associate professor of civil engineering. “This increased roughness not only contributes to premature deterioration of the deck but also presents a stark contrast to motorists traveling on and off the bridge.”
Armed with a $131,370 grant from the Rhode Island Department of Transportation, Gindy is studying the relationship between the placement of steel rebar in bridge decks and the measured smoothness of the deck that carries traffic. She and her students are using ground-penetrating radar to locate the rebar in bridges and a surface-profiling machine to measure the smoothness of the concrete.
“What we’re really trying to do is find the link between the location of the rebar and the roughness of the surface,” Gindy said.
According to the URI professor, rough bridge decks have pervasive cracks that allow infiltration of deicing salts, which is a leading cause of corrosion of the steel reinforcement. Once the steel starts to corrode, it expands and causes more cracks and spalling of the concrete leading to an even rougher surface. As the bridge continues to carry traffic, the interaction between repeated heavy truck traffic and a rough surface amplifies the load applied to the bridge. This continuous cycle, if left untreated, will eventually shorten the service life of the bridge deck.
Gindy said her study will determine the characteristics and proper placement of rebars that will create a smoother ride.
“The more concrete you pour over the rebar, the more it’s protected, but it’s also more expensive,” she said. “It’s a matter of finding the economical balance between the quantity of concrete and a long-lasting, well-performing smooth ride.”
Gindy and students Nicholas Paull of Smithfield, Kelley Wharton of East Greenwich and Theodore Blair of Warwick have already conducted a preliminary assessment of several bridges in the state, and they will continue this work throughout the summer. They will compare bridges of differing ages, conditions and traffic volumes, coastal versus inland bridges, and urban versus rural bridges.
“There are a lot of parameters that go into a smooth ride besides rebar,” Gindy said.
By the end of the year when she provides a final report to the Department of Transportation, including 3-dimensional profiles of the bridge decks she is evaluating, Gindy will make recommendations for the best qualities and construction practices that will result in a smoother ride for drivers. The ground penetrating radar and surface profiler will then be shared with DOT so they can use it to assess additional bridges in the state.
Pictured above: URI engineering professor Mayrai Gindy (right) and students Nicholas Paull and Theodore Blair use ground-penetrating radar on a bridge in Exeter in a project to assess the smoothness of local bridges. (Photo by Joe Giblin)